1. Field of the Invention
The present invention relates to a material for anisotropic magnet that can be obtained by hot plastic deforming, and a method of manufacturing the same.
2. Description of the Related Art
Recently, for motors or electric generators, magnets (rare-earth magnets) including rare-earth elements, such as neodymium or samarium have been widely used. The reason the rare-earth magnets are used is that they have excellent magnetic properties and are relatively inexpensive. Coercivity (iHc) and remanence (Br) are considered as important factors in the magnetic properties.
The coercivity is the magnitude of magnetic field that is needed to make magnetization zero. In general, it has been known that heat resistance is excellent when the coercivity is large.
The remanence represents the magnitude of the maximum magnetization at H=0 of a magnet material. In the case that the remanence is large (high), it is possible to reduce the size of the apparatuses, such as an electric generator, and the cost of the magnets, and as a result, this is considerably advantageous.
Therefore, Nd (neodymium)-Fe (iron)-B (boron) magnets having high remanence have been the most widely used as rare-earth magnets.
On the other hand, a magnet alloy that can be obtained by applying hot plastic deforming to R (rare-earth elements)-Fe—B-based magnetic alloys has been known in the related art (see Laying-Open No. H11 (1999)-329810). In Laying-Open No. H11 (1999)-329810, it is described that an anisotropic magnet having excellent magnetic properties can be obtained by optimizing the composition of an R—Fe—B-based magnetic alloy and the process conditions.
Further, a magnet mainly using Pr (praseodymium) to improve coercivity has already been known (see Laying-Open No. H8 (1996)-273914). In Laying-Open No. H8 (1996)-273914, in consideration of ensuring workability in casting and hot rolling, and high coercivity, a magnet, in which the composition of Pr is limited within 15 to 17 atomic percent, is described (see Paragraph “0014”). Further, it has been known that a magnet having high coercivity can be obtained by applying appropriate heat treatment to a Pr—Fe—B-based alloy (see [Operation] in Laying-Open No. H2 (1990)-3210).
However, magnets in the related art have the following problems for use in motors that are used in a high-temperature environment.
Technically, according to magnetic properties of rare-earth magnets containing the main component of Pr or Nd, the coercivity decreases with the increase of remanence, while the remanence decreases with the increase of coercivity, which is a trade-off relationship. It is difficult to improve both of the remanence and the coercivity.
Therefore, the magnet described in Laying-Open No. H11 (1999)-329810 improves the maximum energy product ((BH)max) by particularly increasing the remanence, however, has a problem in that it can not obtain sufficient coercivity. Further, the magnets described in Laying-Open No. H8 (1996)-273914 and Laying-Open No. H2 (1990)-3210 can obtain high coercivity, however, has a problem in that they can not necessarily obtain sufficient remanence.    [Patent document 1] Laying-Open No. H11 (1999)-329810    [Patent document 2] Laying-Open No. H8 (1996)-273914    [Patent document 3] Laying-Open No. H2 (1990)-3210